Hard disk drives are commonly used for data storage in view of their relatively low cost/bit. However, they are subject to crashes, in which the entire disk drive may be wiped out. For this reason alone, it is both complicated and expensive to create reliable storage systems based on disk drive technology. Other problems with disk drives include their large quiescent power consumption and their inability to randomly access data in parallel.
Although many inexpensive solid state storage schemes have been proposed, few show promise for greatly lowering the price of storage below that of flash. Any such devices would probably be made by standard microelectronic manufacturing techniques, and even if layers of storage could be fabricated very cheaply, the achievable reduction in system cost would be modest, because only a limited number of layers can be stacked on an underlying expensive driver chip.
Electromechanical devices have been considered in the past as storage devices, but they tend to be fairly complex, since each cell must be addressed for both writing and reading. These devices generally involve a cross/point array and, if lithography is employed to manufacture them, several masks steps may be necessary to define the array. This then entails considerable vacuum processing. Thus, electromechanical devices have suffered from many of the same limitations that prevent solid state devices from achieving low-cost storage.
What is needed is a memory device that can be constructed inexpensively (e.g., using a roll-to-roll processing technique), and that lends itself to the stacking of many memory layers.